Despite the high likelihood (75%) of a T315I mutation at relapse on first or second-generation TKIs, testing is not critical for the immediate treatment decision. The most potent TKI, ponatinib, would be the next line of therapy regardless of the mutation status, making the test more of a confirmation than a decision driver.
Related Insights
The treatment backbone for Ph+ ALL is shifting away from intensive chemotherapy like hyper-CVAD. Chemotherapy-free regimens combining blinatumomab with a TKI (preferably ponatinib) are becoming the new standard, showing outcomes that are at least as good as, and likely better than, traditional chemotherapy.
Non-covalent BTK inhibitors like pirtobrutinib are currently approved for use after covalent BTK inhibitors fail. Moving them to the frontline setting, as studied in BRUIN-313, disrupts the established treatment pathway and creates uncertainty for managing relapsed disease, as the standard 'next step' is removed.
BTK degraders work despite most kinase inhibitor resistance mutations. However, resistance to degraders themselves alters the BTK binding pocket so significantly that subsequent targeting with any BTK kinase inhibitor is unlikely to be effective, positioning them as a potential end-of-line therapy.
The development of agents targeting specific mutations like CALR and JAK2V617F marks a move away from the "one size fits all" JAK inhibitor approach. This enables a more personalized, molecularly-driven treatment strategy that was previously not possible for MPN patients.
Retesting for biomarkers with liquid biopsy in the third-line setting is crucial. It can uncover new, actionable mutations that have emerged during treatment or confirm the absence of resistance mutations, potentially allowing patients to benefit from re-challenging with a previously used targeted therapy.
A key clinical nuance in CLL is that not all prognostic markers are static. The IGHV mutation status remains unchanged, requiring a one-time test. However, chromosomal abnormalities like deletion 17p can evolve, necessitating re-evaluation at each relapse to guide subsequent therapy choices and adapt the treatment strategy.
While pirtobrutinib is effective after covalent BTK inhibitors, the reverse is unproven. Starting with pirtobrutinib frontline raises a critical unanswered question about whether patients will still respond to older covalent inhibitors, complicating sequencing decisions, especially for younger patients.
While blinatumomab-TKI combinations avoid systemic chemotherapy toxicity, they are associated with higher rates of central nervous system (CNS) relapses. This necessitates an increased number of intrathecal chemotherapy doses to prevent CNS disease, a critical nuance for managing this 'simpler' approach.
A key nuance in managing ponatinib for Ph+ ALL is a response-adapted dosing strategy. Patients are typically started at a 30mg dose, which is then reduced to 15mg once a good minimal residual disease (MRD) response is achieved. This approach aims to maintain efficacy while mitigating long-term toxicity.
Clinicians are hesitant to use newer, potentially safer non-covalent BTK inhibitors before established covalent inhibitors. While it's known that non-covalents work after covalents fail, the reverse is unproven, creating a one-way treatment path that reserves these newer agents for later lines of therapy.
